i) Field of the Invention
The present invention relates to an ink jet print head for use in a non-impact printer, and more particularly to its nozzle arrangement structure and also to a head driver circuit for the ink jet print head on the premise of the nozzle arrangement structure.
ii) Description of the Related Arts
Conventionally a non-impact printer using an ink jet print head has been known. The non-impact printer can be widely used for a facsimile machine, a plotter, a bar code printer, a digital copying machine and the like. The non-impact printer is provided with a head having a number of fine nozzles, and by blowing fine particles of an ink onto printing medium such as paper or the like from the nozzles, printing is carried out without contacting the head with the printing medium.
In an impact printer for performing printing by contacting a head with a printing medium, when the head is designed, it is necessary to consider a material of the printing medium, and also, when the head is produced, it is required to sufficiently consider the same. The non-impact printer has an advantage that such a technical limitation does not exist. Further, high speed printing is possible by using the non-impact printer.
In FIG. 32, there is shown a conventional ink jet print head. This ink jet print head 10 has a similar construction to one disclosed in Japanese Patent Laid-Open No. Hei 2-266944.
The ink jet print head 10 possesses a flat plate structure. This flat plate structure can be formed by etching a glass plate or the like. The ink jet print head 10 is comprised of an ink chamber 12, a plurality of pressure chambers 14, a plurality of ink slits 16 and a plurality of nozzles 18. The ink chamber 12 is formed in circular shape near the peripheral part of a circular glass plate. The pressure chambers 14 are formed inside the circle. The pressure chambers 14 are formed corresponding to the respective nozzles 18. The ink slits 16 couple the pressure chambers 14 with the corresponding nozzles 18. The nozzles 18 are arranged in a rhombic form near the center of the ink jet print head 10, as shown by a one-dotted line in FIG. 32. In fact, the fine nozzles 18 are arranged on this rhombic form in high density, but this is omitted for brevity in FIG. 32.
In the ink jet print head 10, as a member to be overlapped on this flat plate structure, a pressure generating part 20 is used. The pressure generating part 20, for example, is composed of a piezoelectric substrate or the like, and on this pressure generating part 20, a plurality of electrodes 22 are formed. Each electrode 22 is provided corresponding to each pressure chamber 14 so as to construct a single piezoelectric element. Hence, when an electric signal is applied to one electrode 22, the piezoelectric element of this electrode 22 is excited, and the pressure is added to the corresponding pressure chamber 14. Then, the ink in the pressure chamber 14 is caused to flow in the direction to the nozzle 18 via the ink slit 16. As a result, the ink is discharged from the corresponding nozzle 18. In this case, the plurality of electrodes 22 can not be seen in the state that the pressure generating part 20 is partly cut out, as shown in FIG. 32, but the row of the plurality of electrodes 22 is shown by two broken lines for understanding.
In the ink jet print head, the viscous drag of the ink flowing in the ink slit depends on the length of the ink slit. In this conventional example, since the pressure chambers 14 are arranged in the circular form, the lengths of the ink slits 16 become almost equal. Hence, in the conventional example, the viscous drags of the ink slits 16 are equalized to obtain effects such as a realization of high frequency driving and the like.
However, when the pressure chambers 14 are arranged in the circular form as described above, since the nozzles 18 are concentrated upon the central part of the circle, it is difficult to perform multi-dot printing. The dot is a printing part formed by the ink discharged once from one nozzle. In the conventional example shown in FIG. 32, since the interval between the adjacent nozzles 18 is restricted by the interval between the ink slits 16, the interval between the nozzles 18 becomes large, and as a result, the dot interval becomes large.